Apparatus for cleaning a mercury-dropping electrode of a through-flow polarographic analyzer

ABSTRACT

Solid impurities that accumulate on the mercury dropping electrode of a polarographic analyzer are periodically dissolved by washing with a suitable solvent at prescribed intervals such intervals are chosen to be less than the time necessary for such accumulation to become sufficient to adversely affect the polarographic current during the continuous measurement, in the analyzer, of a test liquid containing such impurities. The solvent is introduced into the analyzer through an input port separate from that used to introduce the test liquid. The washing is accomplished by flowing the solvent over the electrode without immersing it in the solvent.

United States Patent [191 Vesely et al.

[ Dec. 24, 1974 [75] Inventors: Miloslav Vesely; Zdenek Bohac,

both of Pardubice, Czechoslovakia [73] Assignee: Vyzkumny ustav organickych syntez,

Pardubice, Czechoslovakia 221 Filed: Apr. 7, 1972 21 Appl. No.: 242,044

[30] Foreign Application Priority Data OTHER PUBLICATIONS Stock; J Polarographic Micro-Analysis; Chem. Products, Jan-Feb. 1944, pp. 23-26.

Milner; 0., Principles and Applications of Polarography; Longmans Green & Co., London, 1957, pp. 19-22.

Primary Examiner-Robert J. Corcoran [57] ABSTRACT Solid impurities that accumulate on the mercury dropping electrode of a polarographic analyzer are periodically dissolved by washing with a suitable solvent at prescribed intervals such intervals are chosen to be less than the time necessary for such accumulation to become sufficient to adversely affect the polarographic current during the continuous measurement, in the analyzer, of a test liquid containing such impurities. The solvent is introduced into the analyzer through an input port separate from that used to introduce the test liquid. The washing is accomplished by flowing the solvent over the electrode without immersing it in the solvent.

2 Claims, 1 Drawing Figure PATENTEB 85324 I974 APPARATUS FOR CLEANING A MERCURY-DROPPING ELECTRODE A THROUGH-FLOW POLAROGR-APHICANALYZER BACKGROUND OF THE INVENTION ment. Such liquid may typically comprise a solution or suspension having solid impurities therein.

The test liquid from the reaction chamber is introduced through a first input port of the analyzer into a measuring space in which a mercury-dropping electrode is situated. The electrode introduces mercury into the test liquid to electrolyze the liquid and thereby to facilitate the electrical sensing (e.g., temperature, pH, etc.) necessary to derive the required curves.

One disadvantage of such analyzers of this type is that when the test liquid is continually introduced into the measuring space, the solid impurities contained in the liquid accumulate on the mercury-dropping electrode and cause a progressive increase in its electrical resistance. This in turn decreases the current flow through the electrolyzed liquid and impairs the function of the analyzer.

In order to remove such accumulation, it has been necessary in the past to stop reaction and measuring process for significant times to gain physical access to the mercury-dropping electrode for purposes of cleaning, or, alternatively for purposes of disassembly and replacement. The significant down time of the apparatus necessary to accomplish such cleaning or replacement can be particularly deleterious in the common case where the mercury-dropping electrode itself is used as a sensing electrode.

SUMMARY OF THE INVENTION An improved cleaning technique which dissolves such solid impurities on the mercury-dropping electrode and which does not require the stoppage of the reaction-measurement process for long periods is accomplished by the apparatus and method of the present invention. A second input port is provided in the analy zer for introducing a suitable solvent into the measuring space to expose the electrode thereto. The solvent is introduced at periodic intervals smaller than the elapsed time necessary for the accumulated solid impurities to cause a predetermined increase in the resistance of the electrode.

In the arrangement of the invention, the electrode is vertically located above the overflow to prevent immersion and the solvent is flowed over the electrode.

BRIEF DESCRIPTION OF THE DRAWING The invention will be further set forth in the follow ing detailed description taken in conjunction with the appended drawing, in which:

The sole FIGURE is a pictorial representation of a through-flow polarographic analyzer having facilities for periodically flowing a solvent for solid impurities over the mercury-dropping electrode while the latter is maintained above the overflow level in the analyzer.

DETAILED DESCRIPTION Referring to the drawing a through-flow polarographic analyzer designated generally at 21 is adapted in a conventional manner to measure specified characteristics of a test liquid. The liquid is introduced into a first input port 22 from a suitable reaction chamber (not shown). The port 22 communicates, within the analyzer, with a measuring space 4 in which a conventional mercury-dropping electrode 3 is situated. In a manner familiar to those skilled in the art, mercury from the electrode 3 is dropped through the test liquid in the space 4 to effectively electrolyze the liquid for electrical sensing. The liquid is withdrawn from the measuring space through an output port designated generally at 23. The port 23 includes an overflow 5 disposed at a vertical level indicated by the dotted line. The mercury accumulates in a pool 14 at the bottom of the measuring space 4, and such mercury may be withdrawn through a second overflow 16.

The continuous introduction of the test liquid into the measuring space via the port 22 causes the solid impurities in such liquid to accumulate on the mercuryemitting mouth of the electrode 3. The buildup of such accumulation progressively restricts the drop size of the emitted mercury and increases the electrical resistance of the electrode, thereby deleteriously affecting the current through the electrolyzed test liquid.

In accordance with the illustrative arrangement of the invention, there is provided a second input port 24 through which a solvent, suitable for dissolving the solid impurities that collect on the electrode 3, is continually introduced to the electrode 3 mouth space through a tube 1. In the arrangement shown the electrode 3 is positioned in the measuring space 4 above the level of overflow 5. A constricted end 2 of the tube 1 terminates adjacent and above the electrode 3 to flow the solvent over the electrode at periodic intervals. With this arrangement, the electrode 3 may be cleaned without the necessity of immersion in the solvent.

The advantage of the arrangement of the invention over the prior art is that the introduction of the solvent and the washing of the electrode with such solvent may be done without the necessity of stopping this reactionmeasurement process for the long intervals necessary to manually clean and dry, or alternatively disassemble and replace, the electrode 3.

The nature of the solvent is of course determined by the character of the impurity to be dissolved for example, when the impurities are resinous compounds such as dyestuffs which represent the reaction products of a decomposition of diazo-compounds, sulfuric acid is a suitable solvent.

In the foregoing, the invention has been described in connection with preferred arrangements thereof. Many variations and modifications will now occur to those skilled in the art. It is accordingly desired that the scope of the appended claims not be limited to the specific disclosure herein contained.

What is claimed is:

1. In a polarographic analyzer including a first input port, an output port having an overflow port at a first vertical level within the analyzer, a measuring space defined between the first input port and the output port, means for introducing into the first input port a test liquid having solid impurities therein, and electrode means disposed in the measuring space for dropping the electrode means, the solvent flowing over the electrode without immersing the electrode in the solvent. i

2. An analyzer as defined inclaim l, in which the positioning means vertically locates the electrode means above the overflow port, and the introducing means comprises means for flowing the solvent over the elec- 

1. In a polarographic analyzer including a first input port, an output port having an overflow port at a first vertical level within the analyzer, a measuring space defined between the first input port and the output port, means for introducing into the first input port a test liquid having solid impurities therein, and electrode means disposed in the measUring space for dropping mercury through the test liquid introduced into the first input port, the improvement which comprises: means including a second input port for introducing into the measuring space a solvent for the solid impurities; and means for positioning the electrode means within the measuring space to expose the electrode means to the solvent introduced through the second input port to dissolve solid impurities that accumulate on the electrode means, the solvent flowing over the electrode without immersing the electrode in the solvent.
 2. An analyzer as defined in claim 1, in which the positioning means vertically locates the electrode means above the overflow port, and the introducing means comprises means for flowing the solvent over the electrode means. 